The New Psychology of Helmholtz, Wundt, and Stumpf in Germany had its childhood in the era of Romantic medicine and post-Kantian philosophy of Herbart, Hegel, and Fries. Leading the way from Naturphilosophie toward both behaviorism and phenomenology was R. Hermann Lotze (1817-1881), who devoted his early career to a critique of pathology, physiology, and medical psychology. From this critique came a mechanical program for the study of mind: it distinguished mathematical laws, empirically observed processes, and ideal interpretations or purposes in the explanation of disease, life, and consciousness. Thus Lotze was a key transitional figure, whose theories of scientific method, spatial perception, cognition, volition, and cognitive development were carried by Charles Peirce, James Ward, F.H. Bradley, John Dewey, William James, and James Mark Baldwin into the New Psychology of Great Britain and America. The proposed research extends the methods and objectives of a 1975 doctoral dissertation, "The Medical Realism of R. Hermann Lotze," in three respects: (1) in the use of additional European archival material, (2) in the interpolation of additional secondary material on the interaction of medical and philosophical thought, and (3) in the incorporation of new research by the principal investigator on Lotze's contributions to psychological theory.